import torch
import torch.nn as nn
import torch.nn.functional as F
from torch.nn.modules.utils import _pair
from mmdet.core import (auto_fp16, build_bbox_coder, force_fp32, multi_apply,
multiclass_nms)
from mmdet.models.builder import HEADS, build_loss
from mmdet.models.losses import accuracy
[docs]@HEADS.register_module()
class BBoxHead(nn.Module):
"""Simplest RoI head, with only two fc layers for classification and
regression respectively"""
def __init__(self,
with_avg_pool=False,
with_cls=True,
with_reg=True,
roi_feat_size=7,
in_channels=256,
num_classes=80,
bbox_coder=dict(
type='DeltaXYWHBBoxCoder',
target_means=[0., 0., 0., 0.],
target_stds=[0.1, 0.1, 0.2, 0.2]),
reg_class_agnostic=False,
reg_decoded_bbox=False,
loss_cls=dict(
type='CrossEntropyLoss',
use_sigmoid=False,
loss_weight=1.0),
loss_bbox=dict(
type='SmoothL1Loss', beta=1.0, loss_weight=1.0)):
super(BBoxHead, self).__init__()
assert with_cls or with_reg
self.with_avg_pool = with_avg_pool
self.with_cls = with_cls
self.with_reg = with_reg
self.roi_feat_size = _pair(roi_feat_size)
self.roi_feat_area = self.roi_feat_size[0] * self.roi_feat_size[1]
self.in_channels = in_channels
self.num_classes = num_classes
self.reg_class_agnostic = reg_class_agnostic
self.reg_decoded_bbox = reg_decoded_bbox
self.fp16_enabled = False
self.bbox_coder = build_bbox_coder(bbox_coder)
self.loss_cls = build_loss(loss_cls)
self.loss_bbox = build_loss(loss_bbox)
in_channels = self.in_channels
if self.with_avg_pool:
self.avg_pool = nn.AvgPool2d(self.roi_feat_size)
else:
in_channels *= self.roi_feat_area
if self.with_cls:
# need to add background class
self.fc_cls = nn.Linear(in_channels, num_classes + 1)
if self.with_reg:
out_dim_reg = 4 if reg_class_agnostic else 4 * num_classes
self.fc_reg = nn.Linear(in_channels, out_dim_reg)
self.debug_imgs = None
def init_weights(self):
# conv layers are already initialized by ConvModule
if self.with_cls:
nn.init.normal_(self.fc_cls.weight, 0, 0.01)
nn.init.constant_(self.fc_cls.bias, 0)
if self.with_reg:
nn.init.normal_(self.fc_reg.weight, 0, 0.001)
nn.init.constant_(self.fc_reg.bias, 0)
[docs] @auto_fp16()
def forward(self, x):
if self.with_avg_pool:
x = self.avg_pool(x)
x = x.view(x.size(0), -1)
cls_score = self.fc_cls(x) if self.with_cls else None
bbox_pred = self.fc_reg(x) if self.with_reg else None
return cls_score, bbox_pred
def _get_target_single(self, pos_bboxes, neg_bboxes, pos_gt_bboxes,
pos_gt_labels, cfg):
num_pos = pos_bboxes.size(0)
num_neg = neg_bboxes.size(0)
num_samples = num_pos + num_neg
# original implementation uses new_zeros since BG are set to be 0
# now use empty & fill because BG cat_id = num_classes,
# FG cat_id = [0, num_classes-1]
labels = pos_bboxes.new_full((num_samples, ),
self.num_classes,
dtype=torch.long)
label_weights = pos_bboxes.new_zeros(num_samples)
bbox_targets = pos_bboxes.new_zeros(num_samples, 4)
bbox_weights = pos_bboxes.new_zeros(num_samples, 4)
if num_pos > 0:
labels[:num_pos] = pos_gt_labels
pos_weight = 1.0 if cfg.pos_weight <= 0 else cfg.pos_weight
label_weights[:num_pos] = pos_weight
if not self.reg_decoded_bbox:
pos_bbox_targets = self.bbox_coder.encode(
pos_bboxes, pos_gt_bboxes)
else:
pos_bbox_targets = pos_gt_bboxes
bbox_targets[:num_pos, :] = pos_bbox_targets
bbox_weights[:num_pos, :] = 1
if num_neg > 0:
label_weights[-num_neg:] = 1.0
return labels, label_weights, bbox_targets, bbox_weights
def get_targets(self,
sampling_results,
gt_bboxes,
gt_labels,
rcnn_train_cfg,
concat=True):
pos_bboxes_list = [res.pos_bboxes for res in sampling_results]
neg_bboxes_list = [res.neg_bboxes for res in sampling_results]
pos_gt_bboxes_list = [res.pos_gt_bboxes for res in sampling_results]
pos_gt_labels_list = [res.pos_gt_labels for res in sampling_results]
labels, label_weights, bbox_targets, bbox_weights = multi_apply(
self._get_target_single,
pos_bboxes_list,
neg_bboxes_list,
pos_gt_bboxes_list,
pos_gt_labels_list,
cfg=rcnn_train_cfg)
if concat:
labels = torch.cat(labels, 0)
label_weights = torch.cat(label_weights, 0)
bbox_targets = torch.cat(bbox_targets, 0)
bbox_weights = torch.cat(bbox_weights, 0)
return labels, label_weights, bbox_targets, bbox_weights
@force_fp32(apply_to=('cls_score', 'bbox_pred'))
def loss(self,
cls_score,
bbox_pred,
rois,
labels,
label_weights,
bbox_targets,
bbox_weights,
reduction_override=None):
losses = dict()
if cls_score is not None:
avg_factor = max(torch.sum(label_weights > 0).float().item(), 1.)
if cls_score.numel() > 0:
losses['loss_cls'] = self.loss_cls(
cls_score,
labels,
label_weights,
avg_factor=avg_factor,
reduction_override=reduction_override)
losses['acc'] = accuracy(cls_score, labels)
if bbox_pred is not None:
bg_class_ind = self.num_classes
# 0~self.num_classes-1 are FG, self.num_classes is BG
pos_inds = (labels >= 0) & (labels < bg_class_ind)
# do not perform bounding box regression for BG anymore.
if pos_inds.any():
if self.reg_decoded_bbox:
bbox_pred = self.bbox_coder.decode(rois[:, 1:], bbox_pred)
if self.reg_class_agnostic:
pos_bbox_pred = bbox_pred.view(
bbox_pred.size(0), 4)[pos_inds.type(torch.bool)]
else:
pos_bbox_pred = bbox_pred.view(
bbox_pred.size(0), -1,
4)[pos_inds.type(torch.bool),
labels[pos_inds.type(torch.bool)]]
losses['loss_bbox'] = self.loss_bbox(
pos_bbox_pred,
bbox_targets[pos_inds.type(torch.bool)],
bbox_weights[pos_inds.type(torch.bool)],
avg_factor=bbox_targets.size(0),
reduction_override=reduction_override)
else:
losses['loss_bbox'] = bbox_pred.sum() * 0
return losses
@force_fp32(apply_to=('cls_score', 'bbox_pred'))
def get_bboxes(self,
rois,
cls_score,
bbox_pred,
img_shape,
scale_factor,
rescale=False,
cfg=None):
if isinstance(cls_score, list):
cls_score = sum(cls_score) / float(len(cls_score))
scores = F.softmax(cls_score, dim=1) if cls_score is not None else None
if bbox_pred is not None:
bboxes = self.bbox_coder.decode(
rois[:, 1:], bbox_pred, max_shape=img_shape)
else:
bboxes = rois[:, 1:].clone()
if img_shape is not None:
bboxes[:, [0, 2]].clamp_(min=0, max=img_shape[1])
bboxes[:, [1, 3]].clamp_(min=0, max=img_shape[0])
if rescale:
if isinstance(scale_factor, float):
bboxes /= scale_factor
else:
scale_factor = bboxes.new_tensor(scale_factor)
bboxes = (bboxes.view(bboxes.size(0), -1, 4) /
scale_factor).view(bboxes.size()[0], -1)
if cfg is None:
return bboxes, scores
else:
det_bboxes, det_labels = multiclass_nms(bboxes, scores,
cfg.score_thr, cfg.nms,
cfg.max_per_img)
return det_bboxes, det_labels
[docs] @force_fp32(apply_to=('bbox_preds', ))
def refine_bboxes(self, rois, labels, bbox_preds, pos_is_gts, img_metas):
"""Refine bboxes during training.
Args:
rois (Tensor): Shape (n*bs, 5), where n is image number per GPU,
and bs is the sampled RoIs per image. The first column is
the image id and the next 4 columns are x1, y1, x2, y2.
labels (Tensor): Shape (n*bs, ).
bbox_preds (Tensor): Shape (n*bs, 4) or (n*bs, 4*#class).
pos_is_gts (list[Tensor]): Flags indicating if each positive bbox
is a gt bbox.
img_metas (list[dict]): Meta info of each image.
Returns:
list[Tensor]: Refined bboxes of each image in a mini-batch.
Example:
>>> # xdoctest: +REQUIRES(module:kwarray)
>>> import kwarray
>>> import numpy as np
>>> from mmdet.core.bbox.demodata import random_boxes
>>> self = BBoxHead(reg_class_agnostic=True)
>>> n_roi = 2
>>> n_img = 4
>>> scale = 512
>>> rng = np.random.RandomState(0)
>>> img_metas = [{'img_shape': (scale, scale)}
... for _ in range(n_img)]
>>> # Create rois in the expected format
>>> roi_boxes = random_boxes(n_roi, scale=scale, rng=rng)
>>> img_ids = torch.randint(0, n_img, (n_roi,))
>>> img_ids = img_ids.float()
>>> rois = torch.cat([img_ids[:, None], roi_boxes], dim=1)
>>> # Create other args
>>> labels = torch.randint(0, 2, (n_roi,)).long()
>>> bbox_preds = random_boxes(n_roi, scale=scale, rng=rng)
>>> # For each image, pretend random positive boxes are gts
>>> is_label_pos = (labels.numpy() > 0).astype(np.int)
>>> lbl_per_img = kwarray.group_items(is_label_pos,
... img_ids.numpy())
>>> pos_per_img = [sum(lbl_per_img.get(gid, []))
... for gid in range(n_img)]
>>> pos_is_gts = [
>>> torch.randint(0, 2, (npos,)).byte().sort(
>>> descending=True)[0]
>>> for npos in pos_per_img
>>> ]
>>> bboxes_list = self.refine_bboxes(rois, labels, bbox_preds,
>>> pos_is_gts, img_metas)
>>> print(bboxes_list)
"""
img_ids = rois[:, 0].long().unique(sorted=True)
assert img_ids.numel() <= len(img_metas)
bboxes_list = []
for i in range(len(img_metas)):
inds = torch.nonzero(
rois[:, 0] == i, as_tuple=False).squeeze(dim=1)
num_rois = inds.numel()
bboxes_ = rois[inds, 1:]
label_ = labels[inds]
bbox_pred_ = bbox_preds[inds]
img_meta_ = img_metas[i]
pos_is_gts_ = pos_is_gts[i]
bboxes = self.regress_by_class(bboxes_, label_, bbox_pred_,
img_meta_)
# filter gt bboxes
pos_keep = 1 - pos_is_gts_
keep_inds = pos_is_gts_.new_ones(num_rois)
keep_inds[:len(pos_is_gts_)] = pos_keep
bboxes_list.append(bboxes[keep_inds.type(torch.bool)])
return bboxes_list
[docs] @force_fp32(apply_to=('bbox_pred', ))
def regress_by_class(self, rois, label, bbox_pred, img_meta):
"""Regress the bbox for the predicted class. Used in Cascade R-CNN.
Args:
rois (Tensor): shape (n, 4) or (n, 5)
label (Tensor): shape (n, )
bbox_pred (Tensor): shape (n, 4*(#class)) or (n, 4)
img_meta (dict): Image meta info.
Returns:
Tensor: Regressed bboxes, the same shape as input rois.
"""
assert rois.size(1) == 4 or rois.size(1) == 5, repr(rois.shape)
if not self.reg_class_agnostic:
label = label * 4
inds = torch.stack((label, label + 1, label + 2, label + 3), 1)
bbox_pred = torch.gather(bbox_pred, 1, inds)
assert bbox_pred.size(1) == 4
if rois.size(1) == 4:
new_rois = self.bbox_coder.decode(
rois, bbox_pred, max_shape=img_meta['img_shape'])
else:
bboxes = self.bbox_coder.decode(
rois[:, 1:], bbox_pred, max_shape=img_meta['img_shape'])
new_rois = torch.cat((rois[:, [0]], bboxes), dim=1)
return new_rois